This is a Mesa issue. It does not account for VK_EXT_swapchain_maintenance1. In DXVK and vkd3d-proton we override the present on a per-present basis, and it overrides MESA_VK_WSI_PRESENT_MODE.
Thanks for that pointer! Reported as a mesa bug instead: https://gitlab.freedesktop.org/mesa/mesa/-/issues/11379
proton 8.0-5x1 2024-06proton 9.0-2x1 2024-06MESA_VK_WSI_PRESENT_MODEx1 2024-06MESA_VK_WSI_PRESENT_MODE=immediatex1 2024-06
In a wayland session, completely hidden windows running in proton usually drop to 1 FPS, e.g. when having them running in an inactive workspace. For many online games this is a problem as they will also only simulate at 1 FPS. Elden Ring will even flat out kick you from the online session after a few seconds.
As a workaround, there are a couple of env vars you can set to cause that not to happen. I don't know if the former is driver specific, but it works with Mesa's AMD vulkan driver at least:
Setting those environment variables works in Proton 8.0-5, and stops the window from dropping to 1 FPS when in an inactive workspace. But it no longer works in Proton 9.0-2, nor in the current experimental release. In both of those, the FPS once again drops to 1 when the window's workspace becomes inactive.
Borrowing some system stats from KDE's settings and Steam's system info: